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Ok what happens when someone get fewer or more chromosomes I know it has somthing to do with nondistuction but why does nondistuction happen?
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Nondisjunction ("not coming apart") is the failure of chromosome pairs to separate properly during cell division. This could arise from a failure of homologous chromosomes to separate in meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. The result of this error is a cell with an imbalance of chromosomes. Such a cell is said to be aneuploid. Loss of a single chromosome (2n-1), in which the daughter cell(s) with the defect will have one chromosome missing from one of its pairs, is referred to as a monosomy. Gaining a single chromosome, in which the daughter cell(s) with the defect will have one chromosome in addition to its pairs is referred to as a trisomy.
Monosomy is a form of aneuploidy with the presence of only one chromosome (instead of the typical two in humans) from a pair.[1] Partial monosomy occurs when only a portion of the chromosome has one copy, while the rest has two copies.
[edit] Human monosomy
Human conditions due to monosomy:
Turner syndrome - Women with Turner syndrome typically have one X chromosome instead of the usual two sex chromosomes. Turner syndrome is the only full monosomy that is seen in humans—all other cases of full monosomy are lethal and the individual will not survive development.
Cri du chat syndrome -- (French for "cry of the cat" after the distinctive noise by affected persons' malformed larynx) a partial monosomy caused by a deletion of the end of the short p (from the word petit, French for small) arm of chromosome 5
1p36 Deletion Syndrome -- a partial monosomy caused by a deletion at the end of the short p arm of chromosome 1
Most organisms that reproduce sexually have pairs of chromosomes in each cell, with one chromosome inherited from each parent. In such organisms, a process called meiosis creates cells called gametes (eggs or sperm) that have only one set of chromosomes. The number of chromosomes is different for different species. Human beings have 46 chromosomes (i.e. 23 pairs of chromosomes). Human gametes have only 23 chromosomes.
If the chromosome pairs fail to separate properly during cell division the egg or sperm may have a second copy of one of the chromosomes. (See non-disjunction.) If such a gamete results in fertilization and an embryo, the resulting embryo may also have an entire copy of the extra chromosome.
Monosomy is a form of aneuploidy with the presence of only one chromosome (instead of the typical two in humans) from a pair.[1] Partial monosomy occurs when only a portion of the chromosome has one copy, while the rest has two copies.
[edit] Human monosomy
Human conditions due to monosomy:
Turner syndrome - Women with Turner syndrome typically have one X chromosome instead of the usual two sex chromosomes. Turner syndrome is the only full monosomy that is seen in humans—all other cases of full monosomy are lethal and the individual will not survive development.
Cri du chat syndrome -- (French for "cry of the cat" after the distinctive noise by affected persons' malformed larynx) a partial monosomy caused by a deletion of the end of the short p (from the word petit, French for small) arm of chromosome 5
1p36 Deletion Syndrome -- a partial monosomy caused by a deletion at the end of the short p arm of chromosome 1
Most organisms that reproduce sexually have pairs of chromosomes in each cell, with one chromosome inherited from each parent. In such organisms, a process called meiosis creates cells called gametes (eggs or sperm) that have only one set of chromosomes. The number of chromosomes is different for different species. Human beings have 46 chromosomes (i.e. 23 pairs of chromosomes). Human gametes have only 23 chromosomes.
If the chromosome pairs fail to separate properly during cell division the egg or sperm may have a second copy of one of the chromosomes. (See non-disjunction.) If such a gamete results in fertilization and an embryo, the resulting embryo may also have an entire copy of the extra chromosome.